BIOLOGY 3 Marks Question

a. Opioid receptors are present in various regions of the body, including the central nervous system (brain and spinal cord) and peripheral nervous system.
b. Heroin is chemically known as diacetylmorphine.
c. Opioids are extracted from the opium poppy plant, scientific name of the plant is Papaver somniferum.

Variations keep on occurring in each subsequent generation. But most of them may not be retained by the organism because nature may not support such variations. When a particular variation passes the test of natural selection, then only it is inherited in a species in the long run. Hence, it can be said that creation and presence of variation is directionless but natural selection and adaptation are directional.

i. Deletion of the gene for ADA in an individual leads to ADA deficiency disorder Adenosine Deaminase (ADA) enzyme is crucial for immune system to function.
ii. Gene therapy is helpful in the treatment of ADA deficiency.
The treatment involves the following steps:
a. Lymphocytes from the blood of patient are grown on a culture outside the body.
b. A functional ADA, cDNA (using a retroviral vector) is then introduced into these lymphocytes.
c. Such genetically engineered lymphocytes are returned to the blood of patient.
d. Periodic infusion of such genetically engineered lymphocytes is required by the patient.

Commensalism: This is the interaction in which one species benefits and the other is neither harmed nor benefitted. An orchid growing as an epiphyte on a mango branch, and barnacles growing on the back of a whale benefit while neither the mango tree nor the whale derives any apparent benefit.
Mutualism: This interaction confers benefits on both the interacting species. Lichens represent an intimate mutualistic relationship between a fungus and photosynthesising algae or cyanobacteria. Similarly, the mycorrhizae are associations between fungi and the roots of higher plants. The fungi help the plant in the absorption of essential nutrients from the soil while the plant in turn provides the fungi with energy-yielding carbohydrates.

a. Hydrogen bonds
b. Purine base
c. Pentose sugar (Deoxyribose)
d. 5' end of the chain - d

Haemophilia is a recessive X-linked genetic type disorder. Haemophilia is more common among males than females because males only inherit one X-chromosome. There are 46 chromosomes in humans Females have XX chromosome while males have X and Y chromosome. So, male offspring inherit X-chromosome from their mother and Y-chromosome from them father Males only have one X-chromosome and if the X-chromosome and this is the reason that males are suffering from haemophilia is the x - chromosome carries the mutation. While in females as they have so X chromosomes, and this is a recessive disorder.